Telephone-exchange system and apparatus therefor.



M. F. HILL.

TELEPHONE EXCHANGE SYSTEM AND APPARATUS THEREFOR.

APPLICATION FILED JAN.10, I9I8. I

Patented Nov. 18, 1919.

6 SHEETSSHEET I.

M. F. HILL.

TELEPHONE EXCHANGE SYSTEM AND APPARATUS THEREFOR.

AP LICATION FILED JAN. :0, 1918.

'1 ,322, 170. Patented Nov. 18, 1919.

6 SHEETSSHEEI 2.

M. F. HILL.

I TELEPHONE EXCHANGE SYSTEM AND APPARATUS THEREFOR. 1,322,170.

APPLICATION FILED JAN-10.1918.

9 1 Hm ,I E mm 4 m u w 6 H m cm P gwoerl l 01 M. F. HILL.

TELEPHONE EXCHANGE SYSTEM AND APPARATUS THEREFOR.

AP LI ATION FILED JAN-10,1913- 1,322, 170. Patented Nov. 18, 1919.

fiSHEETS-SHEEI 4.

M. F. HILL.

TELEPHONE EXCHANGE SYSTEM AND APPARATUS THEREFQR.

APPLICATION FILED LAN-10. 191a.

- 1 ,322,170. Patented Nov. 18, 1919.

M. F. HILL.

TELEPHONE EXCHANGE SYSIEM AND APPARATUS THEREFOR.

APPLICATION FILED IAN. I0, 1918.

Patented Nov. 18, 1919.

6 SHEETSSHEET 6 UNITED STATES PATENT OFFICE.

MYRON F. HILL, OF NEW YORK, N. Y., ASSIGN OR OF ONE-HALF T0 EDWARD E. CLEMENT,

' OF WASHINGTON, DISTRICT OF COLUMBIA.

TELEPHONE-EXCHANGE SYSTEM AND APPARATUS THEREFOR,

Original application filed March 24, 1908, Serial No. 423,051.

cation filed January 10, 1918.

To all whom it may concern:

Be it known that I, MYRON F. HILL, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Telephone-Exchange Systems and Apparatus Therefor, of which the following is a specification, reference being bad therein to the accompanying drawing.

My invention relates to telephone exchanges, and has for its object the reduction of the wiring and apparatus and the resulting simplification of the exchange.

My invention consists in the substitution of a few circuits controllable by a large number of subscribers for the individual circuits heretofore used in such a way that any person may control at all times one of the few common circuits. More particularly my invention consists in an exchange in which the subscribers are divided into groups preferably of about one hundred each, each group provided with a number of trunk lines reaching from the central exchange to short individual circuits, which in turn are connected to the subscribers station.

For the busiest groups of subscribers fifteen or twenty trunk lines are required, while for the suburban groups but a few trunk lines are required, perhaps-not more than eight or: ten.

This present application is a division of my co-pending application filed March 24, 1908, Serial No. 123,051, issued Jan. 15, 1918, as Patent No. 1,253,688, in which all matters disclosed and not claimed will be claimed herein.

For each group thetrunk lines are divided into two sets, one of receiving trunk lines and the other of transmitting trunk lines. The receiving trunk lines are connected to a single board of the multiple switch board central station. NVhen any subscriber of agroup takes his telephone off from its hook, his individual short circuit is automatically connected to one of the idle receiving trunk lines, and this connection operates an indicator at the board to which the receiving trunk line is connected, informing the operator that a subscriber desires a connection. The operator then finds out the number of the. desired subscriber, connects the receiving trunk line to a transmitting trunk line,

Specification of Letters Patent.

Patented Nov. 18, 1919.

Patent No. 1,253,688. Divided and this appli- Serial No. 211,236.

belonging to the group of the desired subscriber, and automatically causes, by means of a commutator at her board, the transmitting trunk line to be connected to that subscriber.

The transmitting trunk lines of each group are connected in multiple to all the boards of the exchange. Any transmitting trunk line of a group may be connected automatically to any subscriber of that group under the proper conditions.

In the drawings,

Figure 1, represents in diagram view the plan of th circuits of the exchange.

Fig. 2, shows the automatic switches which interconnect the subscribers circuits and the trunk lines of a group, and the circuits by which they are controlled.

Fig. 3, shows in diagram view the connection of two transmitting trunk lines to two boards of an exchange, and the substitute for a multiple switch board test circuit.

Fig. 4, shows a face view of a section of the board, to which the transmitting trunk lines of a group are connected.

Fig. 5, shows in sectional view one. form of an indicating spring jack.

Fig. 6, shows a vertical sectional view of a different form of an indicating spring jack.

Fig. 7 shows a sectional view of a third modification.

Fig. 8, shows a plan view of a transmitting terminal switch, and the circuits by which said switch is controlled.

Fig. 9, shows the commutator outfit of a central ofiice operator by means of which a transmittine trunk line is connected to a subscribers circuit.

Fig. 10, shows in side view part of the circuit controller.

Fig. 11, shows an edge view of the apparatus which controls the operation of a trans lnitting trunk line switch.

Fig. 12, shows in side view, a transmitting trunk line switch.

Fig. 13, shows a portion of the same in plan view.

Fig. 14, shows an end view of part of the commutator apparatus.

Fig. 15, shows a. side view of part of the operators cord switch with the plug removed.

Figs. 16 and 17 are modifications.

Fig. 18 is a detail.

Fig. 19 is a diagram of the telephone switch hook in normal position.

Fig. 20 is a similar view of the hook in act ated position.

I ig. 21 is a diagram of the mechanical line relay in one of its actuated positions.

Fig. 22 is a similar view of the relay in another one 'of its actuated positions.

In Fig. l are shown two boards of a multiple switch board exchange to which are connected receiving and transmitting trunk lines. Ts, T82, T83 are transmitting switches by means of which the transmitting trunk lines T15, T25 and Tt are connected to short f individual circuits A, A, A B B, &c. To each of these short individual circuits A, A, A B, B, &c., are connected subscribers outfits like that shown in diagram view in A".

The two wires a and Z) of the short metallic circuit are normally connected to bells a, contact a switch lever a normally connected thereto, and back to the wire 6. When the telephone 0: is switched for use, the circuit is transferred from the bells a, to the subscribers telephone a secondary coil (1, contact a and switch lever a temporarily connected thereto.

The local circuit including the contact'a, primary coil a, transmitter a, battery a, and contact a is closed at the same time.

The two wires are open to each other while the switch lever a is in transit between the contacts a and a. When the telephone is removed from the hook the usual automatic spring device causes the heel contact a of the switch lever to strike the insulated con-- tact a, on the lever a, thus grounding the wire 6, through the switch lever a heel contact a insulated contact a, condenser (1 and ground at G. i

The lever is then released and the projection a of insulating material prevents the contact a from touching the contact (L13. Vhen the telephone is restored to its hook, the contact a insulated from but mounted upon the switch lever (1 comes into contact with the lower surface of lever (Z12, thus grounding the wire a, through the tension spring a. hen the hook is released the insulated projection o prevents a connection between the contacts a and a". ,Thns when the rear end of the switch hook lever a moves downward, the metal at a engages the contact plate a without striking the metal at a; and when the rear end of the lever a moves upward, the contact plate a engages the metal o without striking the plate a.

The telephone a has a flexible cord sup port a, secured to a contact spring (1 adapted while the telephone is suspended therefrom to make contact with the contact point a, thus closing the circuit of the bells a, in a shunt around the telephone circuit a, a, while the telephone is switched for use.

The purpose of this device will be seen later. The wires a, Z), of the short individualmetallic circuit, are connected by multiple branches 0 and (Z to each receiving switch R9 and transmitting switch of the group to which the subscriber belongs. These connections are shown in Figs. 1 and 2. The form of switches in Fig. 2 is preferred. Those in Fig. 1 are simplified to better illustrate line circuits.

The branches 0 and (Z are connected to the contacts 0 and cl, on each switch. On each switch are ring contacts 0 and (Z in juxtaposition to the contacts 0 and d, and adapted to be connected thereto by the contacts c and (5 respectively, mounted upon the circuit closing lever of each switch. To

the ring contacts 0 and (l are connected two wires 0 and d of the metallic circuit of each trunk line.

The connection between a subscribers metallic circuit and a receiving trunk line Rt is effected as follows: \Vhen the sub scriber removes his telephone from its hook thus switching it for use, a circuit is closed from the ground G, condenser (1 contacts a and a switch lever a line conductor 1), to the automatic sub-central switches, in dividual branch wire 6, coil 0, contacts e conductor 6 common to all the subscribers of the group, conductor 6 to the central exchange, current generator D, and ground G.

Upon the energization of a current from the battery B energizes the relay 6, over the circuit including relay e, resistance 6 (about equaLto that of the magnet 6 contacts e e resistance 6 thus releasing the escapement e ofthe weight or motor a The motor a propels at a regular speed the shaft f, upon which are mounted the receiving and transmitting switches R8, R82, Ts and T8 A resistance 6 graduates the amount of currentsupplied to the relay 6*.

The alternating current on the circuit just traced energizes the coil 6' as shown in Fig. 21, which produces a change in the circuits, so that the subscribers line will secure a connection to one of the receiving trunk switches but no other. As the coil 6 is energized, its core attracts the armature of lever 6". Since the upper end of lever e is in contact 'with the contact plate e mounted on the lever c it slides on a plate which acts as a cam lifting the lever 6 until the upper end of the lever 6 leaves the plate 6 Then the lever 6 drops again, its insulating plate resting on an upper end of thelever e, and the metal of the lever resting against the rear of contact 6 At the same time, when the coil 6 attracts the lever e, a contact portion on the front of contact engages the spring contact 6 and the rear portion its of the contact e is withdrawn from con.- tact with the back contact 6 From this mechanical operation it will be seen how the following electrical circuits are established; their object being to connect the subscribers line to a receiving trunk line exclusive of any other trunk line connection.

From one pole of battery B by way of magnet e, resistance 6, of which there preferably one individual to each subscriber, contacts a and a now closed, wire 6?, branch wire 0, of switch R82 for example, contact e individual to the subscribers circuit, (see Fig. 8), brush contact 2', coils i of the magnet operating the circuit closer in, wire 2' brush contact 2', ring contact a, common to the sets of contacts of all the subscribers of the group, wire 6", containing contacts 6 normally closed, there being a separate wire 6" and separate contacts 0 for each receiving switch, wire e to bat tery B.

The same circuit might be traced through any other receiving switch belonging to this rou in case its travelin arm and cuit closers will be in position to make con tact with the subscribers line simultaneously,

To effect this the sets of contacts of a subscribers line, line a?) for example, are arranged in the same vertical line, while the normal positions of the circuit closers h are arranged spirally, or at differentpoints around the shaft Presuming that the circuit closer 7t and switch arm h of the switch R5 make connection with the contacts of line at, the coils i of the magnet will attract the armature if, operating the circuit closer It so that the contact 0 crosses the contacts c.

and c the contact (Z crosses the contacts Z and (Z and the contact 2" makes connection with the individual switch board contact a, closing the following parallel circuits:

From one side of the coils 2' through wire i, contact 2", contact 6, branch wire a, wire 6, coil 0 individual to each sub? scriber, to battery cult isthe same as previously traced over wire a.

ii he coil 6 when energized opens the temporarily closed contacts 0 and a by lifting the armature. This releases the armature and contact a by removing the stop contact e, which has been engaget with the contact a so that it falls back toits normalposition except that it does not strike contact a on account of the in The rest oi this cirii'ig switch, R8 for example, no other re-.

ceiving switch R8, or transmitting switch Ts, or T82, can be connected toit,

The circuit of the subscribers line a, b, when thus connected is-continuous through the two limbs c* and (Z of the receiving trunk R25 to the central station (see Fig. 1), Where these limbs are connected, through intermediate switch apparatus controlledfby the operator, to the two contacts a and d of a connecting plug P.

It the subscribers line a, 6, had been connected to any other trunk line of the group, R15, for example it would have been connected to another plug, through another set of switching apparatus controlled by the same or another operatoiywho may be sta- .tioned at board N0. 2, or elsewhere.

It a subscriber of another group had taken his telephone off his switch, subscriber No. 309 for example, connected to line B he would have been connected to a receiving trunk line R25 for example, and thus con nected to a plug I controlled by an oper 4 tor at board No. 3, as shown.

It will be noticed that the short individual metallic circuits A, A, A and A belonging to subscribers No. 201, No. 241, No. 241-2 and No. may be connected through receiving trunk lines R23, and RF, to switch plugs P under the control of an operator at board No. 2. These subscribers lines are but a few of the large number, ona' hiti-idred for example, which may be connected through these switches .19 and Rs; There may be additional switches R3 and corresponding additional trunk lines Rt, to which the same subscribers lines may be connecteth in like manner the short individual. inc tailic, circuits belonging to subscribers No. 309, No. 310, No. 311, No. 322 and No. 313, lettered B B, B", B and lit-may be connected through one or more receiving switches R8 to one or more receiving trunk lines Pet and thence to plugs at central. The subscribers lines referred to are but a Y of the number that may be employed. .1 reterably however there are one hundred less subscribers lines adapted to be connected to plugs P at board N o. 3.

In like manner I divide all the subscribers of the exchange into groups of one hundred 01" 1mm: 9 and s0 w f1 Thus a conveys-m 1mm 0f mu sm't from the @ubscrflwer 1e subscriber infnrms the whom he desires to be cow 3252; for exzunple.

b Arts the ping P into n am uuwt 0mg in mmmitting; 89 T2? for emmqleq adapt-ed to be llhl'ni ,Kh w runsl'nitting switch siam't outlying: n'mxmliic cilcljlii; r This cmmection is V in. now

wmdrmi um cmnmuhm 12,1 SL711 Fem-M1911; DA'JBYEIJQTQd. 100 m' 0W1 under 300 are (:onnwi mi. m board 1%.

1 9W liners numbered 23% (zofilmec't ed mation 1! v and the n amt manly r, u; know mun-m a. W111i Hue plug has tion that each strip g touches a contact spring or springs 03 and after leaving these springs touches one or more contact springs 0 The last strip 9" which passes under all the contacts 0 and (Z is so formed that it touches the contact spring 0 while it touches the contact spring (1". thus simultaneously cross connecting these springs. When the plug P has been placed upon the cross bars 2 of the sets of cross bars 0 and d. and the cylinder C rotated once as described, the contact springs c" and (1 connected to those two cross bars are connected to the contacts 0 and d by the four longest strips successively as described, establishing the following circuits, which may be traced upon Figs. 1 and 2:

from ground G through the alternating current generator D, a supply wire 0 reaching to the sub-central to which line No. 322 is connected. thence through contacts (2 condenser e to the relay a, wire 6. including the set of normally closed contacts a, (the order of the relays and contacts be ing immaterial) thence by trunk line conductor (5*, to spring jack contact 01 plug contact ll, contact. spr ng (1, contact point (i wire d contact (1., one of the contact springs d", the one connected thereto by the cross bar 2, of the set designated 2i, thence by way of plug P connected thereto, to ground at G. This circuit is made and broken four times by the strips g of the commutator. The relay (2 is energized four times. Referring now more particularly to Fig. 2, it will be seen that when the relay 6 is energized it accomplishes two functions, in connection with the selecting and controlling a p'aratus there shown, which is located at t is sub-central station to which the called line is connected.

Not only does it actuate the ratchet movement m of the units switch but it actuates the circuit controller C When the armature of relay 6 is drawn down, its heel e forces the link 6 upward, which in turn tilts the rocker 0 against 'the offset m. This offset is rigidly connected to the ratchet wheel operated byv the pawl m and resists the rocker a so that the rocker which is pivoted on the pawl 31% lifts the pawl upward. As seen in Fi 10, it catches the next tooth 0f the rate et wheel and when the relay e is deenergized, the controller C is advanced one step. With it travels the offset m, which travels downward and no longer resists any oscillations of the rocker e. and this operation is not re sated.

This local circuit is closed our times as stated. The first time that the magnet e is energized, the circuit controller C closes the contacts-n, n? and n through the respective contact plates. The operation of the circuit controller C by-the second and third closing of this circuit is prevented as described. The functions of these sets of contacts will shortly be described.

\Vhen the circuit is closed four times the relay operates the ratchet mechanism m propelling the contact arm m around to contact o. 2 on the units switch m As has been described after a strip has left a contact spring (l it makes contact with a spring 0, grounding the 0 side of the circuit as follows From ground at G, current generator D, supply wire 0 contacts 6 normally closed, condenser es, relay e, contacts 11 closed as described, trunk line conductor a, jack contact c plug contact 0, contact spring. a, contact point 0 commutator contact 0, strips g, cont-act spring a" connected to bar numbered 2, plug P, and ground G. This circuit is also energized four times.

The relay 0 therefore attracts its arma-- ture four times thus actuating the ratchet mechanism m and propelling the contact arm m around to contact No. 2 of the tens switch.

The fourth time that the circuit is closed, the relays e and e attract their armatures together and thus by means of the heels c and links a". force upward both ends of the rocker a, forcing the pawl m upward so as to catch the next tooth of the ratchet 12.. When the relays are de'energized the rocker and pawl are released, and operate the controller another step, bringing it to its third and last position. Thus it opens the contacts n and n and closes cont-acts n and n by altering the position of the respective contact plates 11, a n and a It is to be noted that the pawl m acts on its back stroke and not onits forward stroke. Its back stroke in the diagrammatic illustration of Fig. 2 is the downward stroke, but this showing is for convenience of diagram only, since in the practical apparatus shown in Figs. 10 and ll'the back stroke of pawl m is an upward stroke. i The closing of contacts n establishes a circuit from the grounded direct current generator D over the supply wire e through the restoring magnet M to the trunk line conductor 0 When this line is connected to'ground by a subscriber or by an operator,

the magnet M attracts its armatures m and by means of mechanical connections, m" for example, withdraws the detents m and m permitting all the switching apparatus to be restored to its normal position.

When the armature m is attracted the insulated wedge m opens the contacts e and e. This prevents relay 6 for example,

i in" eontaet Eli ple. OI Whenever a snhsei'ihei' hangg e his telephone TPCClTPK upon its mi'iteh, thereby oz using the eontzn-te a antl to come into elevti'ieal connection. {II'Ol'lDKilZ'ig' the eonilnetor m iiireetly through spring (19 when the arniatin'e m is attracted by the restoring magnet M, it closes the set of eontaetn we, grounding the eii'enit lllt'lll(lllll' relay iit' through wire of and three hi'aneh circuits one h "2111011 or containing contacts of ClOSSti except when the controller is in its normal positioi'i shown, a second ln'aneh. m containing" eontznrtn m elosed exeept when the ratchet m, is in its normal positioi'i, and the third h 'aneh m containing eontaete in closed under similar eonditions. The corn taets m1 and 912 are closed when the cleft wheel attached to the ratchet :an'ies the cleft beyond the eontavt spring As long a anyone of the three braneh circuits is eioeeti while restoring, the reht Iv will keep ail the oletents m", in, and m, Withdrawn from their appropriate 'atchets, thus in snring a l'ellu'tll of all the switches to their normal position.

'lhereitore Whenever a subscriber hangs up his telephone the opp-Mates eonti'oliingg a. t *ansinitting" switch is restored.

To return new to the manner in "which this sn'iteh apparatus controls the o iieiration ot tt transmitting tirnnlc switch Ts.

The first step 'toi'wai'd of the eontiollet t3 closes the set 01') contacts n as ileseiihei't.

This eloses the following cite-nit including magnet. )z1ttei'y B, magnet efl-iesistanee m one m contacts n Wire, me, Wire a, hack to battery Thie niatn t at once releases the esczipenient em the shatt 01 illlOUR'? f to rotate nnttei." the i thienee ot the motor 0" so that the titttl "n lllitlliilgj with the Sl'lft. t,

i switch 'lfs" rotates anti is really to close any circuit itlt'itltfl tho eontrol ot' the unit nit tens switeh t' l hen the contacts nine elosett been (leseriheit, end when. the. owns m m rest upon the oontaeto 2 of the snitohes tepi'esentinpg snhsei'ih n' l lo the following circuit is estalfi "wow-inn 772 eontaet of transmitting ewiteh To contact in on hot in -anti wt from the sn'i' Wii'e eoiis 3: 1 thence by Way o the eontaet 5, contact 6" oil? the e pniiot' eoiwv 6: a, open line (1 i is eonn :1 any oit B Wiping eo. ehaitt f, en iteh let r nl eleett neetetl V ntaet e eontaet on Witch m a: m ot the switch eontt ots n now the. oi too it eontt 1G by the not hath to the on it own. mt,

This til'Citj J he eloeetl onl when t switch own it ot the tllttIlSllUiL i M VH2. then 1. it touch it y it Con ti e" eonies into n the set ot eontaetn ot' the .HttltDfiCi'iiJUt' 1m purpose {it iilnstiatinn t a transmitting" en'iteh r tion between a tennt: iine amt n. ttll lkst'iiiifil fi lllM. the line a F is iepresentml 1E,

heioiing to snhsam'ihei' him tor einnn ile, t'lflti the group ot switehee its and "til ma he re- {ifttHlOt'l tempo *aiily as representing the an toinatie snhwenti'nl ot the 300 gibonp, lVhen therefore the ahote eiienit is established the :n'inatine it ot the switch "to" is attraeteil 'ansing the contacts 0 and (e to crops connect the contacts 9 anti at with the ring contacts 0* and, (47* respectively. A circuit is thus estahlishecl between the snhseiihers line and the transmitting trnnl; line. Another t ans nitting sn'iteh T3 is controlled by another trunk line Ti the local. en'eni'e oi whieh are not shown but which are the duplicatesof those eonneetecl to and C(Hltl'OllGll by the trunk T25". It has been tteserihecl hon an. ope 'ator has mused a eonneetion liietween a tiai emitting tt'nnlt line lit and n oalletl subscriber. It necessary thnt the ()E'ititiftttOl shouhi. know that this circuit has heen tahliehett When the lifting of separation of the e Zita contacts i @Lfiti o i the ai'inat-in'e opening the no ltlai'inp; nieiateti .t'. really been (lescrihetl I? tor piece P pii'otetl. snlatetl arms; 1 eonn e tll'ltl M" with the eont end at sanie tine at w taet springs 0 end ti tie and a At the name hase P" tliseoiineotn the antl i .f'oni the iii-thing; the tol a i l nncl (Z i hate a nil nu to the Ht ilk H e i .i one eon n oeteil in not "iote plug contacts 0 and d to the conductors c and (Z of the trai'ismitting trunk, thus establishing a complete circuit for conversa tion. As long as this circuit remains intact the indicator c informs the operator that the lines are busy.

If however, a called subscriber is already connected to another transmitting or receiving trunk line, this trunk line described cannot establish connection with him, for the reason already stated in connection with the description of the magnets e, e, and the levers e' and c. The operator noticing that the called subscriber is busy informs the calling subscriber to this efi'ect, and he may drop his receiver without hang ing it upon its hook and wait for the called subscriber to finish his. engagement. Dropping his receiver in this way leaves it hanging upon the cord 09" thus causing the spring contact a to come into contact with. the contact a" closing the circuit of the call device a in a shunt around the telephone set. When the busy called subscribers business is over his line is automatically connected to the calling subscribers line without the intervention of the central operator, and both subscribers are called up automatically. This automatic connection depends upon the condition of the circuit of the called subscriber; As long as it is connected elsewhere the contacts 6 are open. Whenthis connection is dissolved the contacts e are closed, the transmitting trunk line switch Ts is operated, closing the circuit between the trunk line and the subscribers line, energizing the coil 0 of the operators outfit at central, causing thi trunk line to be connected to the receiving runk line, to which the calling subscriber is connected through the contacts 0 and d", causing a current from the supply generatpr CG to actuate the call device a, polarized bells for example, of the calling subscriber. At the same time the op erator is informed of this connection by the attracted flap of the indicator 0.

Th operator may at any time by closing the pairs of contacts 0 and d by means of normally open key contacts cut her telephone into the circuit, to determine by listening in, the condition of the line, or to.

talk with either subscriber.

The indicator 0 indicates busy? as long as a circuit remains established, but as soon as a circuit is opened by the operator or either subscriber in disconnecting the circuits, and grounding the'b-limb, this indicator releases its flap, indicating the disconnection to the operator.

When a subscriber hangs 11 his telephone and the restoring relay .L 4 attracts the armature m." which releases the ratchet mechanism of the three switches m ,m and C as described, the plate '21 opens the contacts n thereby releasing the armature 7&2 of the transmitting switch Ts, so that this switch disconnects the subscribei"s line a, 'b, from the transmitting trunk line Tt'. The weight of the armature h causes the catch h to become engaged with a detent 7& which causes the arm h to be carried around again, by the shaft which is turning under the influence of the motor (1 \Vhen the transmitting switch closed the circuit between the subscribers line a, b, and the trunk line Ti the contact 2' coming into contact with the contact 0 closed a parallel circuit from the wire 2", through the relay e to the battc ry B, opening the contacts 6 and e and 6 v The opening of contacts 6 prevents the sulbscriber from getting a different connection while connected with. The opening of contacts 6 and a prevents another trunk line T25 from being connected to the same subscriber, so, that while two subscribers are connected together for conver-' sation by an operator their circuit cannot be interrupted or interfered with by another slubscriber or-any other operator or the same operator over another trunk line. When the operator who has established the circuit closes the contact 0 or when either subscriber hangs up his telephone, the 0 side of the established circuit is grounc'led thereby restoring the transmitting switch apparatus, as described by means of the relay M and at the same time establishing a circuit from the grounded current generator calling subscriber from the receiving trunk line Rt.

Summing upthe operations alread described, they are briefly as follows: eferring to Fig. 1, subscriber No. 201 for example, desires connection with another subscriber No. 322 for example.

Subscriber No. 201 removes his telephone from its switch lever thus establishing a connection over a receiving trunk line Rt for example, to the operator at board No. 2 to which the receiving trunk line is connected. The trunk line indicator e indicates the call, and the operator removes the plug P from its resting placcl thus introducing the operators telephone set into the trunk line and restoring the indicator 0" to its normal condition.

l hc subscriber in the usual manne in forms the operator that he Wishes to talt: With No. The operator thug connects the trunk linc plug to a transmitting trunlt line T9 for example, at a trunk switch scction numbered 3, and by operating her commutator outfit causes that trunk line to be connected to the ('lesirecl subscriber. She does not select a transmitting trunk line in use at another board on account of a inultiplc switchboard busy test which will be described later. The operator then turns her cord switch lcrcr P and gives her attention to other calls. The indi ntor c at once indicates Whether the desired connec tion has been established and it it has been, the called subscriber's bells are auto1natically rung. lt the called subscriber is bi m the calling; nibscril'ier mag, Wait With hi phone at his ear, for the desired connec .7 1 or he may drop his telephone and return to his Work in which case, when the called subscriber is through the connection between the called and the calling sul'iscriber is automatically established and. the be is out both rung.

When either subscriber hanf; up his phone, he disconnects the entire circuit, ant the indicator 0 at central role 1: it: in torn'iin g the operator of the CliBC'OHIIBC ll both subscribers shaulcl by accident it to operate the restoring; apparatus of the sub-central st-vitches the 0 J61; tor inaj m as soon as she ascertains this tact by list in restore the apparatus by closing the con tacts 0 Fig. 3 shows a test system which may be used with my ll'lV&I1tlOI1,'Lllhl'10llQ;l1 it obvious that am suitable test sf stern may be used in place. Two boards are shown, board and. board 3. At each board is a spring iaclr ill, for each of two transmitting trunk lines T5 and Each jaclt ton 12/ tains the contacts and a already scribed and a third contact j. The test tact of all the jacks connected to a tra Initting trunk line are connected together by a test "wirej Eachcont-actj is connected to a testbattery J through individual coils or lan'ips j and the other pole of the test tery is connected to a third contact J on the plug P ot each receivin q' trunk li The plug? also has contacts a and are? ihed, The contacts in Fig". l, hat (lill'erently arranged iron, the conta ts in Fig. it. This arrangement lies Within the skill ol the ell-metrical smith ncer. When a plug is; inse- ,t in c iach: as shown, a. circuit establ' herd train the i ll ovct Wire 7 to the contact i of ln l igr. ti lSliCWZH no form of the jaclt J, This inch has a test contact y", the two line contacts a and d i'iaounted upon the in sulated support of an incandescent lamp j, but insulated therefrom. This lamb y" is u. small lamp of the Edison or any other type, and is mounted to the rear of the switch, hole and just beyond the reach of the plug P. Each lamp is preferably provided With a reflector j adapted to reflect the light strongly out of the switch hole of its jack, and out of no other switch hole. The rehector may be mercury on the glass itself, and a projectin tube 5 provided to exclude the light from other jacks.

In Fig. 6 there is another form of jack. In this figure the lamp j is incloscd in a long reflecting or non-rcflecting cylinder 3' adapted to exclude the light from other jack holes. The jack contacts 0 and d and j may be mounted in any suitable Way. In Fig. *l is a third form of jack. In this jack is a coil j hzwin an aperture j" to permit the passage of light from one or more lamps f with reflectors j. The lamps and re .tleetoi i one or both, may be individual to cacl 1h. 0?. common to two or more jacks, and should be constantly burning, so that non l y the jacks are lighted. When,l1oweven the coil is energized by a closed test circuit as doscribcch the core j attracts the magnetic finger j, attracting the fin j shutt oil the light from the jack iolc, rcntlerin it dark, which in this form of jacln indicates the line to be busy.

l prefer him'ei'er the forms shown in Figs" 5 and, 6. Although I show this jack for a busy test, that to :aihow that SUbSOTlbGl. is to begin conversation, that a, coiwersatmn in progress, or that it is over, it is obvious that it may be used for other purposes, that is lot calling for clearing out, for trunl li e signal-work, and various sin'iilar purpo i In li ig. =l are shown a number of jacks, three of which indicate busy. This is a section of one of the switchboards to which all the transmitting trunk lines of group No. Q, are. connected. By inserting a plug in any one. of these jacks, the operator con.-

a connection between a transmitting tr-tuiilt line and any subscriber of the 200 group.

'llhc switcl ihoard divided into sections ll. to this To each. section are con nected the transmitting trunklincs of a ditl'orcnt group of subscribers, and each section irked with the appropriate number of ioup we all ly been described howa trans- "ttfitl. liigwfl elicit lu nil Peril 0 and 0 common toall the subscribers of the group and connected to the trunk line conductors 0* and d as shown in Figs. 2 and 12. The line Wires a?) of each subscriber are connected to a different pair of contacts c' and d.

The contacts and e are connected to the wires c and e and c respectively, there being a different set of those wires for each subscriber as shown. There are ten cont-acts a one of these contacts being common to ten subscribers Each contact c is connected to a contact upon switch 111. The contact numbered'O is connected to the contacti'narked 0 upoii the switch on. The contact c numbered 1, is connected to the contact m numbered 1, etc. The contacts 6* are connected tothe contacts of the switch m Contacts a numbered 0 are connected to contacts O of the switch. (ontacts numbered 1 are connected to contact No. l of the switch, etc. The set of contacts belonging to each subscriber comprises individual contacts 0, (2", a, 0 and 11*. The ring contacts and (Z are common to all the subscribers connected. to the switch. Each contact c is common' to a different set of ten subscribers. Contact 0 for example, is common to subscribers 0 to S) of the group. Contact 3, for example, is common to subscribers 30 to 39 of the group, etc. So that the switch m" selects the unit of a subscribers number and the switch m selects the tens thereof. Foreach subscriber there are separate contacts (2 and resistance c.

The functions of the circuits and apparatus have already been shown in connection with Figs. 1 and 2.

Fig. 9 shows the operators conunutator outfit already described or illustrated in diagram in Fig. 1. Upon a plate of insulating material C are mounted cross strips of conducting aterial (Z Through each strip d pr ject push buttons C so mounted as to slide up and down through the strip and through the support C The strips (Z are separated from each other by insulating material C Each push button C has around its neck a spring C, O e end of which is soldered to the push button and the other end soldered to the strip upon which the push button is mounted. soldering is not necessary but is preferred on account of the .good electrical connection which results therefrom. The lower end of each push button is provided with a point and hollow portion C and when a button is pressed down as shown at C it separated two conducting bars,- C and 0 thereby separating them and then by meansoi the hollow described permits them to return almost to their normal position, holding the push button in its operative position. When another push button is depressed and the are again separated this push button This" C is released and the other one is held in its place. If the same push button is again depressed it will spring back as far as the notch C and there be held a second time. The bars are at each end mounted upon but insulated from a support C, which is connected to the insulating plate by toggl -joints, Thu-' these bars with their support form a kind of gridiron. The mounting of but one corner of this gridiron is shown but the other three corners are similarly mounted.

The conducting bars are at both ends mounted upon and electrically connected with a support C which is mounted by means of toggle-joints C upon the insulating plate (3. A cord C attached to the toggle-joints C running over the pulley C, and connected through a spring 0 to a weight C holds these gridirons in their normal position with the )ost 0 touching thetoggle-joints, to keep them in a normal position.

Pivoted upon the bar C is a lever 0 one end of which is pivoted to the movable bar C and the other end of which carries an insulated stop C Against this stop normally rests a stud or roller C secured to the commutator wheel C, holding the commutator in its normal position. Vhen a push button C is depressed, it moves the bars C mounted upon the cross bars C which in turn causes the lever C to remove the stop C from beneath the roller C, releasing the commutator Wheel C. A key C with studs C causes the friction clutch C to turn on its axis C and by means of the spring connection G causes the commutator wheel C to turn in the direction of the arrow. As the bar C returns at once to its normal position when a push button has completed its downward movement, the catch C is restored to its first position so that when the commutator C has completed a rotation the stud or'roller C ,Will prevent it from turning any farther. The shaft C may be used in common for several or all commutators, and is regulated to prevent a too rapid motion of the con'nnutator. The commutator wheel O is mounted loosely upon the shaft C' but prevented from longitudinal movement. The shaft C is rigidly connected to the key C Upon the body of the commutator C are mounted the posts or rods 9 adapted to cross connect the strips cand d with the contact springs 0 and (8 respectively. The last rod 9 to pass under the springs is so wide as to electrically connect all of the springs simultaneously to the strips 0 and d. The rods 9 are double, and have cuts so that one rod alfects or strikes' only spring contacts a, and the other rod strikes contacts d. The rods g" are so related to the springs that all the springs 0 and d" strips to tact 0 an insulated support C which 0' 5b plug should have a handle.

with

eti'ilie d 2 tive e etyuetioh t oopei'zu U the hotter forced into ooh and 31 1 A; molly i'est upol' LOtl C hovered with ordinary iuhhei" .1 i is mounted eoeh end u C pivoted at U to the in the arm U and against the C adjusts the position of the I'l'illElfS Wit relation to the (BOlDHlUtilllOl rods.

The strips 0 and a me mounted upon. iected at either end to supporting spring U". which in turn is mounted upon the base t Through oath sprii'ip; U passes the she of a screw U having; threaded end Work-- it? ing in a threaded hole in a rigid support C.

In this manner the proximity of the strips to the contact springs may he from time to time adjusted to allow for Wear, end eo fortl. The function of these parts has 30 already been described. The purpose oi? this figure is simply to show the preferred hieoha-nioal construction of the commutator outfit.

Upon a push button. 43 ie mounted a pin G Dlljfili a slot i3 There inu p he a s ept: slot ifi lioieach push huttoii.

A. portuin oi the keyboard is shown. In other parts are omitted as they are 1116.1.6

"" duplicetiou.

There are iutendedto be ten i'oWs eaeii containing ten buttons, adapted to inalize one huiidfed difl'ereht conihinations illustrated in dizigi'ani in Fig. l, and wired as 45 shown in that figure. Instead of e separate button for each number there 111a be one button only adapted to be inserted in any one of one hundred holes. This button would be substantially then a plu Such a the lower end is necessary. r

In Figs. 10 audit-are the n some of the lleteilsiotthe"eonstl'uction oi the transmitcuidioated in If i The hollowin e devious Ml.

5 it for the cii'ou iii l iew h oeojiuitione h, it e]: e

lleii: of mounted iii t. i

"i L-r1uted lily a pawl in in the diree ..ie'ai1ow lit its lioru'ai'd llltw ,inent. pawl m is pivoted upon a. lev r W whi h in turn pivoted when a "uitahle rigid supsort i The pa on ie moulded with a JllET 7 which eiigi atges u the tooth next helow its uorn'ial position shown), and with upmiiil under the influence lhe fixed i'olle'i' a acting pawl so guides the pawl that it may slid .uto position to engage a ratchet tooth, and when the tooth moves the Wheel forward, guided out of engagement wi h the tooth at the moment that the letout i engz z gee the Heft". tooth for detention. The roller H alto iuei'el'ite further useless upward momen'leut oi the pawl. This roller T may permit the aivl to remain in the wheel and a. ineirhanical eonnee-- tion with the d t W' .hdiaw the pawl thin the ratchet i eel While restoring. as The Weight 9" attached to the min. 6* of the pawl tends to draw the pawl into engageuu it With the ratchet teeth, yet is strongly eounteraeted normally (or when the level: at" is not subjected to an outside or magnetic force) by the Weight hung upon the lever P The detent e is mounted upon a suitable pivoting support m t, and upon its heel m is proi 'ided with the insulating Wedge m adapted to open contacts 6 and eff. hut'th'is opening does not happen until the detent has been 'i\"i tl1Cl-3i-1'W"li to its extreme position l :una'gnet Mt This is due to the flexiy of the springs resting against the Wedge m Upon the detent w is mounted a slot to in which plays a rod 9* which in turn. is can ried by the armatuie m so that when the ai'i'natl'zi'e is drawn up by the magnet M it Withdraws the detent T from the ratchet wheel, permittiiugthe latter to return to its normal position. The slot 112- is euffieiently long to permit the detent to p ay over the ratchet teeth in their progress forward with out afleotingg the rod '1" The lifting o? :11- mature m" by the magnet closes oon'taets m the function of th nomads being do SOTllIIGtl in eoumwion "with i a. 2,7narx1ely to Upon the pawl m, see Fig. 11, is pivoted.

a cross bar 6, having loose engagements r with the ends of the armatures r, pivoted at 1'", and acting under the influence of magnets e 'and e. The armatures r have pawl movements m, m, like that shown and described in Fig. 10 for the control-r} ler C".

These pawl movements actuate the ratchet wheels m", upon each of which is mounted an arm m and m? adapted to sweep over and make contactwith studs 09 shown in Fig. 2. In Fig. 11, only stud m" is shown for convenience, on each switch m and m".

These ratchet wheels also have pulleys m with their cord "springs and weights 1',

v r and 0' They are also provided with dedetents.

tents m and'm" having slots m in which works the rod '1 "which withdraws the detent from their engagements with the ratchets. Upon the hub of the ratchet wheel n. is a bar m normally resting against the upper sideof the pivoted cross bar or link e. When this switching apparatus is operated, first the magnet e is operated once, then the two magnets are operated alternately a determined number of times, to correspond with the units and tens of the number signaled, and then the two magnets are operated simultaneously by the double rod 9' shown in Fig. 9. When magnet'e' is o rated the first time it draws down the paw m so that it engages with the proper tooth, and at the same time tips the link 6 so that the other end of the link the right end in the figure, strikes against the bar on and the 'further movement of the link forces the pawl m downward so that it engages with i the next tooth for operating purposes; When their appropriate positions, butdo not affeet the pawl m'on account of the lost inotion of the link connections '1', and on account of the different position for the stop bar 111. due to the advance of the ratchet wheel n to which it is rigidly connected. Finally however the impulses wind up with simultaneous ones, one in each magnet and together they again draw the pawl m down sufliciently to engagewith the next tooth of the ratchet wheel n, thus advancing it another step into its third and final position. The condition of the contacts 11., n, n, n. n and n in these three positions have already -fisa Thev succeeding alternating impulses over themagnets and the correspond.

been described in connection with Fig. 2,

and it is not necessary to repeat here. It is enough to say that the projection upon the two faces of the wheel n should be so.

placed and 'gaged as to accurately perform their proper functions.

Upon insulatingsup spring contacts m an m normally out of engagement with the flanges of the respective pulleys-m on account of cuts or depressions at m" and m respectively, but when the wheelsare not in their normal position these s rings are in contact with the flanges. This 0 oses the circuit to ground from'the s rings to the grounded supports m for t e purpose of retaining the armature m" in its active position untll the wheels are all -restored, as fully described in connection to be rotated under the influence of some kind of motor is rigidly connected a collar rts n are mounted h. This collar supports on .the shaft the mounted collar h. Upon the shaft o'mounted rigidly a second sleeve 11 and also the yoke hof the coilsi as also shown in'F i .18. Each annature yokeih on the shaft is rigidly connectedtheretom'nd acts as armature for", the ma etcoils suspended below it. -Each coil' a-pole b looself s .so shaped as to attract a ring armature h.-

"The poles h bear against a shoul-derfh rigidly connected to the 'floosely 'mounted sleeve h. The ring armature h has an aperture sufiiciently large. tofpermit it to work up and down over the sleeveh' 'Whcn this ring armature is initsu perpdSition, it im 'inges against the shoul er h"? and is there prevented from coming'into con tact with thepoles h of the magnet, which at the time ma be rotating under the influence of the s aft and motor. The armature h is pivoted at' h upon ,an' upright sup'port h" which is mounted upon the switch arm 72.. The switch arm is rigidly. connected to the sleeve k. Connected to the-armature h is a catch h normally enaged: with a catch h. rigidly connected to t e collar h. When the armature h is not attracted the catch h drives'the switch arm 11' and all parts-mounted thereon in the direction in which it rotates. When the-catch h leaves the catch It the switch; arm 71; stops its rotation, while the shaftifithe collar h, the sleeve h and the coils? continue to rotate as long as they are influenced by the motor. Upon the switch arm h" are mounted the contact springs z", 2' and i. The contact spring i is electrically con nected with the switch arm, but the others are insulated therefrom except for the electrical connections. These springs play over the contacts 6*", c and whose functions have already been described. Mounted upon but insulated from the armature b are two hollow rods it, one of which carries a bridging contact the other of which carries a similar contact 0. These bridging contacts are pivotally mounted upon the bars 11. The upper end of each of these contacts normally rests against stop 72. under the influence of springs it.

One end of each spring h is fastened to the bar around which it is coiled. and the other end of the spring is connected to the upper end of the contact mounted upon the bar. One bar it has an extension h which is guided by a properly formed guide piece it, which is mounted upon but electrically insulated from the switchboard h". Mounted upon but electrically insulated from the bars I: is a spring contact i adapted to make connections with anyone of a. number of contacts e around the switchboard.

Upon the support 12 are mounted two contact springs It adapted to make sliding contact with round annular rings lz" mounted upon coils 2' of the magnet. These rings h form the terminals of the magnet coils. One contact spring It is connected by means of wires 2' to the contact springs 2' and z". The other contact spring it is connected by means of wire 2' to contact spring A receiving trunk line switch is identical in construction with the transmitting switch shown in Fig. 12, except for the extra contact a, sprinw i, the construction of contacts 0 and the electrical connec tions. This difference is well shown and described inconnection with Fig. 2.

The circuit closing apparatus in Fig. 12 is shown in its active position. Normally the weight of the armature k causes the catch h to engage with the catch it and the contacts 0 (l and i" to be out of connection with their respective switchboard contacts.

Fig. 13 shows a top perspective view of the apparatus shown in Fig. 12, or at least a part of this apparatus. The sets of contacts of the various subscribers are shown, and the serrated edge h which guides the end it so that the circuit closers c and d make proper connections with contacts 0' and d. It is also shown how the contact springs i, z' and 2' make connection with successive sets of contacts. The moment the spring leaves one set of contacts they make electrithe contact spring 71 mounted upon insulating material. This spring 2' is so adjusted that it will slide easily into place.

lVhen the coils '1? of this switch are energized over the circuit which has already been described, the armature it is attracted by the poles h causing the end h to strike the serrated guide 71. and steer the contacts G and (1 into such a position that they will make proper connections. In Fig. 12 it is shown how the two ends of the pivoted contacts c and (I bear against their appropriate contact surfaces. By means of this construction these contact pieces have a frictional action in attaining their position and an equal amount of pressure is brought to bear upon each of the four pairs of contacts.

Normally these circuit controllers rotate with the shaft They may travel over the switchboard at the rate of at least one rotation in three seconds. This speed has been found successful with solid core slow-acting magnets, but with quicker acting magnets a higher speed may be attained. i

In Fig. 15, is shown a side view of the operators cord switch, the front. view being shown in Fig. 1. The lever P is pivoted at P and is provided with a base P, upon which the plug normally rests. A spring P having bends I working on the edge of the base tends to hold the base in its upper or lower portion against the stops P The operator may tip the lever P into its upper or lower position, thereby altering the circuit connections as described'in connection with Fig. 1.

The generator D which supplies the current for restoring the system should supply a direct current preferably soitoned down by electromagnetic resistance and shunted by condensers as to be inaudible in the receivers by induction. It should be so toned as to be inaudible in the receivers in the manner well known to electrical engineers, by impedances and condensers, and the subscribers bells a so constructed as to respond thereto. The current may be direct, and the bells of the circuit breaking variety; or the current may be alternating of a periodicity below 16 pulsations a second, and with the intermission between the pulsation less than one hundredth of a second in length. This nature of current I prefer. When developed from a dynamo, and its irregularities properly toned down, it acts satisfactorily both as calling and signaling current.

The operation of the exchange with a current supply of this character is as follows:

A subscriber desiring a connection takes down his receiver, thus permitting his switch to ground the 6 side of his metallic circuit, and operating the first receiving switch whose contact springs pass over this subscribers set of contacts. As these switches are spirally arranged with respect to the various sets of contacts of this subscriber, as shown in diagram in Fig. 1, but one receiving switch will operate.

This receiving switch making connection with the calling subscribers circuit closes a complete metallic circuit from the central station to the subscribers station, including the subscribers telephone set, the metallic circuit conductors of the subscriber, and the metallic conductors of the receiving trunk lines, between which is bridged the current generator CG, including a call annunciator c. The current from the generator operates this call annunciator over the circuit described, calling the attention of the operator to this receiving trunk line.

The operation of the receiving switch has prevented the possibility of the calling subscribers line bein connected with any other trunk line, and t e telephone switch of the subscriber has closed the telephone circuit.

The operator, seeing the call annunciator display a signal, takes up the plug of the trunk line associated therewith and this cuts her telephone set into circuit, to find out the number of the called subscriber. Having learned the number she inserts the plug into the jack at her board of a transmittmg trunk line runnin to the group to which the called subscriber belongs, and depresses a button 0 of her commutator outfit shown in Fig 9,

causing the metallic conductors of the trans-- mitting trunk line to make connection by means of the switch apparatus shown in Figs. 2 and 11 with the metallic conductors of the called subscribers circuit. This connection will take place only when the called subscriber is free.

When the operator has thus inserted the plug in a jack and presses her commutator button, she tilts the switch p into the third position already described, and leaves the lines to take care of themselves.

If the called subscriber is free, the transmitting trunk line will immediately connect itself thereto. The tilting of the operators switch P has cut the current from the receiving trunk line circuit just described and introduces it and the annunciator G into the circuit of thetransmitting trunk line as described, so that when the metallic circuit of the trunk line is connected to theoalled subscribers line, this enerator is in a complete metallic circuit, and the annunciator a" is again energized indicating to the operator that the called subscribers line is accessible. With the rela d it closes the me tallic conductors of the receiving trunk line connected to the calling subscriber, thus completing a metallic circuit for conversation.

When the current traverses the circuit of the called subscriber it operates his call bells as long as his telephone is not switched for use. When he answers. the call this current is inaudible in his telephone.

.liis order has been fulfilled and t iat he has been connected to the called subscriber.

The circuit may be supervised by the operator who has established these connections by looping or /bridging her telephone set into the circuit as already described.

. The pulsations of the alternating current CG are preferably so slow as not to cause annoyance to the called subscriber. Five or six pulsations to the second is quite sufficient for the purpose of calling and signaling.

When conversation is over, and the subscribers have no further use for the metallic circuit which has been described the ,subscribers hang their telephones upon their switches thereb roundln the H side y g a of their metallic circuit. his ground connection may be effected by either subscriber or by both. That is, when the a. side of the circuit is grounded by the first subscriber who hangs up his telephone, or by both when they both hang up their telephones together, the relays M and M are operated as has been described with relation to Fig. 2, and'the switches at the sub-central'or, in other words, the transmittin and receiving trunk line switches, are re eased, and the connectionbetween the subscribers metallic circuits "and the trunk line metallic circuits is opened by the disconnected contacts 0' and d thereby opening the circuit of the generator current from CG, and releasing the flap of the annunciator 0" indicating to the operator at the central station that the trunk lines are no longer in use. She then withdraws the receiving trunk line plug from the jack of the transmitting trunk line jack, and returns the plu to its normal restlng place on the insulate sup'portP', at the same time pressin this support back to its normal position s own in connection with the receiving trunk line Rt.

The relay M opens the contacts a" of the receiving trunk,lme switch. v

The restoring circuit operates magnet M which as will be seen in Fi 11, releases the apparatus controlling t e transmitting switch. The contacts n are opened by the circuit controller C thusopening the circuit of the coils i of the transmitting switch, whereby that switch resumes its normal position, and if the shaft f is rotating, it continues to rotate with it.

The s eed with which a connection is establishe by my system depends upon the speed of rotation of the transmitting and receiving switches, and the speed with which the apparatus controlling transmitting switches is operated by the operators commutator outfits.

As the first one of the spirally arranged receiving trunk switches closes a subscribers circuit to central, this circuit is closed alst ,stantaneously. When the exchange is at its busiest time, this connection cannot be delayed more than two seconds at the outside, so that when a subscriber takes down his telephone from its switch, the connection to central is established, and the call annunciator operated before the receiver reaches his ear. The operators telephone is cut in b her taking up the trunk line plug, and tliis is done in the usual manner, except that it is done more quickly than when the operator has to insert a plug into the jack of a calling subscriber. This opera tion is saved by my-system.- After inserting the plug into the jack of the proper transmitting trunk line, and at a glance she can see what trunk line is not busy, she presses down one of her commutator buttons C and after one or two seconds tilts the handle of her switch P This is plenty of time for the apparatus to be operated for controlling the transmitting trunk switch, for one second I find is the outside limit for the maximum number of impulses to be sent over each side of the metallic circuit, so that the time which has been consumed between the moment when the subscriber took down his receiver to the moment when the operator has finished her art in establishing the desire connection is at the outside not more than four seconds, and is, generally not more than two or three seconds. The operators share of this time is still less.

If the called subscriber is free the connection to his line will be almost instantaneous, never more than two seconds later, and this connection is indicated to the operator. If,- during the busy hours of the exchange, the operator has other connections to establish she can at once turn her attention to them. If the called subscriber is busy, the indicator will not 0 erate, and she will know that the connection has not been established. She can then loop or bridge her telephone into the circuit and tell the calling subscriber that he may drop his telephone, and that he will be called when the called subscriber is free. The calling is automatically efl'ected without further attention of the operator when the called subscriber is free. If the'indicator tells her that the connection has not been established after some time, and the trunk line is needed, the operator may close a pair of extra contacts a" and withdraw the plug from the jack, leaving the trunk lines and trunk switches in their normal positimi.

It will be seen that my invention saves a great deal of time on the part of the central operator.

For an exchange of ten thousand subscribcrs having a single central station, each board of the. systems now in use requires a jack for each subscriber and about one hundred annunciators. A dozen or fifteen clearing-out annunciators are also used.

In my exchange, the jacks are reduced from 10,000 in number to 1200 or 1500, the calling annunciators are entirely omitted, and about 12 or 15 annunciators used for both calling and clearing-out.

In systems now in use, 24 to 30 plugs are required for each operator. In my system the plugs are reduced to one half the num- In systems now in use, the metallic circuits of the above exchange would be 10,000 in number, and each one would reach from the subscribers station to the central office. In my system these circuits arereduced to about 1000 to 2500 in number for the greater part of the distance. A

To obtain these advantages requires that each operator shall have a commutator outfit like that shown in Fig. 9 and that from 10 to 25 trunk line switches be located at some outlying points in proximity to grou s of subscribers. That is, each group of en scribers shall have a few switches in some place in their locality. These are the only additions required by my system.

It is obvious that single circuit lines may be organized into an exchange of this kind,

and that by slight alterations two or more.

subscribers may use the same individual cir- ,cuit. For the latter arrangement suitable automatic calls should be provided under the control of the operator.

It is obvious that the subscribers may be called manually by the operator in the usual way, both with two or more subscribers on an individual circuit, or with buttons subscriber on each circuit. But the automatic feature saves time.

It'is also obvious that some of the circuits, those whose subscribers are in close proximity to the exchange, may each have appropriate jacks at the exchan c, with suitable busy test, adapted to be dlrectly connected to receiving trunk lines. Such an arm ement re ulres the usual plug outfits, with some ad cation.

One double plug outfit may occasionally be of use to the operator to connecttogether two lines that have not just called.

Such an outfit is composed of two plugs each rovided with theswitch apparatus shown in Fi. 1 in connection with trunk line Rt, and t ey must be connected together where these outfits join thetrunk line conductors.

In the following claims I shall make use itions, described in another appli- 

